The conventional sprinkler head includes a tubular body that is connected to a water line and defines a water outlet. A pair of support arms extend outwardly from the body and are joined together at a junction. A water deflector is then joined at the junction either permanently or on sliding rods. A cap or closure encloses the outlet in the body and a thermally responsive release mechanism interconnects the cap and the junction. One common form of thermally responsive release mechanism is a frangible glass bulb. The glass bulb provides a direct and stable release mechanism that generally requires fewer parts and less complicated assemblies than sprinklers with other forms of thermally responsive release mechanisms. With a sprinkler head incorporating a glass bulb, the bulb will fracture when exposed to a predetermined elevated temperature, thereby enabling the water pressure in the water line to release the cap. The water will then be directed from the outlet in the body against a deflector and deflected or spread in the desired pattern.
A sprinkler head as used in residential dwellings should have a quick response, meaning that it should release quickly for the objective of a residential sprinkler head is to save lives, as well as property protection. The response time of a residential sprinkler is measured in seconds and the reduction in response time of just a few seconds greatly improves the ability to control and subdue a residential fire in the initial stage, with its life threatening elements of heat, smoke, and noxious fumes.
In a typical glass bulb sprinkler head, the elongated bulb extends vertically or perpendicular to the ceiling. In a concealed mode, working components of the sprinkler head are positioned above the ceiling, with the glass bulb situated above the support arms and deflector, so that the lower end of the glass bulb may be up to one inch above the ceiling. During a fire, smoke and gases of combustion will rise and flow along the ceiling so that the area directly beneath the ceiling is at the highest temperature. Because the glass bulb of the typical concealed sprinkler head is mounted vertically, with the lower end of the bulb located a distance above the ceiling, the response of the typical concealed glass bulb sprinkler head is relatively slow.
A residential sprinkler should also be as inconspicuous, or as aesthetically appealing as possible. Two types of sprinklers have been developed by the fire protection industry in an effort to satisfy these requirements. The concealed sprinkler type, mounted above the ceiling, and the flush type, mounted even with the ceiling, with only the thermally responsive release mechanism extending down from the ceiling. At present there is no approved residential flush-type, glass bulb sprinkler.